Conventional known vibration mode determining apparatuses comprise a vibration measuring means having multiple sensor inputs, a means for calculating a transfer function, and a means for visualizing and outputting the vibration mode (for example, Patent Literature 1).
Further, conventional known apparatuses for analyzing the sensitivity of the control-parameters of an electric motor control unit comprise an electric motor attached to a machine; a detecting means for detecting the amount of motion of a subject constituted by the electric motor or the machine; a command unit that generates a command signal, and a control device that receives the command signal so as to drive the electric motor. The apparatus comprises an open-loop frequency response characteristic measuring means that measures an open-loop frequency response characteristic including no characteristic of the control device; a control device model of the control device of the electric motor control unit; a calculating means that calculates a one-round open-loop frequency response characteristic from the measured open-loop frequency response characteristic and the control device model; and a sensitivity analyzing device that analyzes the sensitivity of the relation between control-parameters of the control device and changes in the one-round open-loop frequency response characteristic (for example, Patent Literature 2).